designing 500 VA sine wave inverter

[manishpatel]

i m designing 500 VA sinewave inverter using pwm.
my pwm frequency is 6 khz, i m using push pull configuration in power section
i want to know whether same type of transformer (12-0-12/ 220V) is used for square wave inverter and sine wave inverter( PWM freq is 6 khz)?
if different type of transformer is required for sine wave inverter, then, what are the specifications of that transformer required?

please reply on my mail id : manishpatel_79@yahoo.com

right now i m using center tapped transformer (12-0-12/220V)
my problem is if i connect bulb of 80 watt it lights very dim.
primary current is only 2.2. amp
i m using 12V 36AH battery for testing

to drive 500 w load properly what i should do?
where can b the problem?
what should i check?

please reply

 

[chuckey]

If you are using a 12V battery then your peak waveform will be 12V across one half of the transformer. So its stepped up to 220V peak on the secondary, when you filter this waveform how do you expect to see a 220 v rms sine wave? Up your supply to 12 X 1.4 = 17V and it might just work or get a different transformer (12/1.4 ~8V, 8-0-8 /220V)
Frank

 

[manishpatel]

thanks for reply
with 12-0 -12 transformer i get 230 rms sine wave on output.
but my problem is 60 w bulb is glowing properly ( i.e. inveter is prividing 60w output)
but as i increase load (80 or 100 W) bulbs are not glowing properly(very dim), my primary current is very low -2.2 Amp only. so power is not transferred from battery to transformer secondary.
how should i increase primary current of transformer?
my main question is " is same transformer can be used for sinewave inverter (6.5 khz PWM) and square wave inverter(50Hz)?"
if they are different ,what type of transformer i should use?

manish

If you are using a 12V battery then your peak waveform will be 12V across one half of the transformer. So its stepped up to 220V peak on the secondary, when you filter this waveform how do you expect to see a 220 v rms sine wave? Up your supply to 12 X 1.4 = 17V and it might just work or get a different transformer (12/1.4 ~8V, 8-0-8 /220V)
Frank

 

[Audioguru]

A mains transformer is designed for 50Hz or 60Hz and some work poorly at 6kHz. Audio transformers with good high frequency response are bifilar wound.

Your PWM frequency is low enough to be very audible and causes the filter to be poor. Manufactured pure sine-wave inverters use a much higher frequency that cannot be heard and a small transformer with a ferrite core. The output filter works well.